CID to SMILES Converter
In short: Resolve compound IDs to canonical SMILES strings for chemistry workflows. It is free, works in your web browser and needs no download.
Convert PubChem CID values to canonical SMILES identifiers.
Input and output formats
| Input: PubChem CID | Output: SMILES | |
|---|---|---|
| Full name | PubChem CID | SMILES (Simplified Molecular Input Line Entry System) |
| What it holds | The Compound ID of a record in the PubChem database. It is looked up to get the structure. | Atoms, bonds, rings, charges and stereo as one line of text. No coordinates. |
| File or form | A whole number like 2244 | .smi or plain text |
File Format Explained
PubChem CID is a numeric compound identifier used by PubChem. It points to a database record rather than directly encoding molecular structure.
SMILES is a compact line notation for molecular connectivity. Converting CID to SMILES is useful when a database gives a PubChem ID but your drawing or cheminformatics tool expects a structure string.
CID lookup depends on PubChem records. Different compound records, salts, isotopes, or stereochemical forms may have different CIDs and SMILES strings.
About PubChem CIDs
A PubChem Compound ID (CID) is the numeric identifier PubChem assigns to each unique chemical structure in its database. For example, aspirin is CID 2244 and caffeine is CID 2519. Papers, supplier catalogues, and datasets often cite CIDs, but a number on its own does not tell you the structure. Converting it to SMILES gives you an editable structure string.
How to use it
- Enter one CID (digits only, no "CID" prefix).
- Run the conversion to fetch the canonical SMILES from PubChem.
- Copy the SMILES into MolDraw, a spreadsheet, or another converter.
FAQ
Is a CID the same as a CAS number? No. CAS Registry Numbers are assigned by the Chemical Abstracts Service and have a hyphenated format such as 50-78-2; CIDs are PubChem's own sequential numbers. Why does a salt give a dotted SMILES? Salts and mixtures contain separate components, which SMILES writes with a dot, for example [Na+].[Cl-].
Next steps: draw it with SMILES to Structure or get an identifier with SMILES to InChIKey.
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